Landscape360°

Brown Patch Fungus in Florida Lawns: How to Stop It Before It Spreads

September 11, 2025

A Florida Fungus That Moves Fast

In North Florida, a healthy lawn can decline overnight. Yellow rings appear, fade to brown, and spread fast—classic signs of Brown Patch Fungus (Rhizoctonia solani). This disease thrives in humid, warm conditions, attacking lawns across Alachua County when irrigation, nutrition, or airflow fall out of balance.

For HOA communities, commercial landscapes, and homeowners, these spots signal more than appearance issues—they indicate underlying turf stress. At Allegiance Landscaping, we prevent fungus through a systems-based approach that aligns irrigation, fertilization, and cultural practices with science and local law.

Brown Patch Grass Fungus

 

Understanding Brown Patch Fungus

Brown Patch is a soilborne fungus that activates when:

  • Days reach 80–85°F
  • Nights dip into the 60s
  • Humidity or dew lingers through morning hours

These conditions are common from late summer through early winter. Rhizoctonia primarily targets St. Augustine, Zoysia, and Bermuda - the turf staples of Gainesville landscapes.

Early Warning Signs

Early detection saves turf and money. Watch for:

  • Circular or irregular yellow patches hat expand rapidly
  • Dark-bordered lesions on individual blades
  • "Doughnut" patterns with green centers and brown rings
  • Turf that pulls up easily from stolons, revealing rot

Unlike drought stress, diseased turf feels damp and may emit a musty odor.

Why It Happens

Brown Patch outbreaks stem from management missteps more than weather alone:

  • Overwatering or night irrigation keeps leaves wet too long
  • High nitrogen fertilization fuels weak, fungus-prone growth
  • Low mowing heights and poor airflow trap humidity
  • Compacted or poorly drained soil holds moisture near the roots

Addressing these root causes is the foundation of long-term prevention.

Brown Patch Grass Fungus

 

How Allegiance Landscaping Prevents Outbreaks

1. Smart Irrigation Management

We program and inspect systems to water only in early morning hours, allowing blades to dry by mid-day. This minimizes leaf wetness—the main driver of Brown Patch.

2. Ordinance-Compliant Fertilization

All nutrient applications follow Alachua County's Fertilizer Management Ordinance (Sec. 77.20–77.31) and Florida Statute 403.9337:

  • No nitrogen applications July – February
  • No phosphorus – unless a verified soil or tissue test shows deficiency
  • When allowed, use ≥ 50 % slow-release nitrogen
  • Never apply on saturated soil, before rain, or within 10 ft of waterbodies (3 ft with deflector)

These rules, grounded in UF/IFAS and FDACS guidance, protect both turf and local waterways.

3. Correct Mowing Heights

Following UF/IFAS standards reduces canopy stress and promotes airflow:

  • St. Augustine: 3.5–4 in.
  • Zoysia: 2–2.5 in.
  • Bermuda 1–1.5 in.
    Cutting lower weakens stolons and increases disease susceptibility.

4. Airflow & Canopy Management

We thin shrubs and lift tree canopies to lower humidity at the turf surface. Homeowners can help by pruning dense areas around patios or fences where air stagnates.

5. Routine Turf Monitoring

Each Allegiance visit includes photo documentation and field notes uploaded to property profiles. Regular inspections allow early intervention—often weeks before visible damage appears.

If Brown Patch Appears

Act fast but strategically:

  1. Pause all nitrogen fertilization until recovery
  2. Switch irrigation to morning-only cycles
  3. Prune surrounding vegetation for airflow
  4. Avoid mowing wet, infected areas
  5. Request professional evaluation

Our licensed partners apply FDACS-approved fungicides when warranted, and we often follow with core aeration and balanced nutrition to help lawns fill in. Damaged blades won't green again—new growth restores the color.

When It's Most Active

Expect peak activity when daytime temps hold near 85°F and nights cool into the 60s—usually September through November. During this period, both communities and homeowners should review irrigation schedules and confirm that controllers match seasonal needs.

Quick-Reference Checklist

Brown Patch Prevention Essentials

  • Water before 9 AM; never at night.
  • Maintain UF/IFAS-recommended mowing heights.
  • Follow fertilizer blackout: No nitrogen July–February.
  • Use ≥ 50 % slow-release N in legal months.
  • Prune for airflow and light penetration.
  • Schedule fall irrigation and turf audits.
  • Inspect after humid or rainy weeks.

Keep this list handy—on a clubhouse bulletin or fridge—as a quick reminder of prevention priorities.

Why Early Detection Saves Thousands

Brown Patch kills stolons quickly. Once roots decay, turf must be replaced—costly for HOA budgets and homeowners alike. Consistent monitoring and ordinance-compliant maintenance prevent those losses and sustain property value year-round.

Key Takeaways

  • Brown Patch develops under humid, warm, poorly drained conditions.
  • Prevention hinges on early watering, airflow, and balanced nutrition.
  • Nitrogen is prohibited July–February under Alachua County ordinance; phosphorus only with proven deficiency.
  • Allegiance Landscaping's integrated management safeguards both turf and environment.

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